Thermoplastic styrenic resin composition

ABSTRACT

The present invention relates to a thermoplastic styrenic resin composition comprises a styrenic copolymer comprising 15-100 parts by weight of a unit derived from a styrenic monomer (i-1), 0-45 parts by weight of a unit derived from a vinyl cyanide monomer (i-2), 0-40 parts by weight of a unit derived from a copolymerizable vinyl monomer (i-3) other than the above monomers, and 0.0005-1.0 parts by weight of a unit derived from a polyfunctional maleimide monomer, all based on 100 parts by weight of the total amount of (i-1) to (i-3). The thermoplastic styrenic resin composition manufactured in the present invention is excellent in processability. The rubber modified thermoplastic styrenic resin composition of the present invention gives a good heat stability, impact strength, fluidity and other mechanical properties. In addition, it also gives a uniform wall thickness, and the gloss on the surface of injected products after painting process is excellent. The thermoplastic styrenic resin composition and the rubber modified thermoplastic styrenic resin composition in this invention are applicable for electric and electronic articles and they are especially applicable for the forming and processing of refrigerator plates. So, the thermoplastic styrenic resin composition and the rubber modified thermoplastic styrenic resin composition of the present invention is beneficial to the industry is also commercially valuable.

BACKGROUND OF THE INVENTION

[0001] 1. Filed of the Invention

[0002] The present invention is related to a thermoplastic styrenicresin composition comprising a specific styrenic copolymer (A). It isfurther related to a rubber modified thermoplastic styrenic resincomposition containing said styrenic copolymer (A) and rubber particle(B). The thermoplastic styrenic resin composition and the rubbermodified thermoplastic styrenic resin composition have high fluidity andexcellent processability such as vacuum forming.

[0003] 2. Background of the Invention

[0004] It has been known that the thermoplastic styrenic resin arewidely used in the manufacture of electric and electronic article aswell as automobile parts because of characteristics on processing andmechanical properties, especially the better appearance and gloss.

[0005] Usually, the thermoplastic styrenic resin could be processed bysuch methods as injection, extrusion, blown molding, etc. As regards tothe process such as vacuum forming, the styrenic resin should beextruded to form sheet in advance, and it is processed into the requiredshape by vacuum forming. For improving the vacuum formability, the resinshould have high melt tension, namely having high molecular weight, toget better thickness uniformity and dimension stability in vacuumforming. The increased molecular weight will, however, normally decreasethe fluidity, processability, and productivity, etc.

[0006] The improvement of both vacuum formability and fluidity could beachieved by adding branching agents, as given in Japanese patentpublication such as 59-149912, 2-182711 and 8-269137. Generally, thebranching agents added are polyfunctional vinyl monomers, such asdivinyl compounds (for example divinyl benzene) or polyfunctionalacrylic ester. In the case of these monomers applied in the process, thestyrenic resin has well-balanced fluidity and processability (ex. Vacuumforming). But the cross linking will be easily occurred and the resinwould be adhered to the wall of pipeline and generate contaminations.Furthermore, with the increase of continuous production time, theabove-mentioned problems will become even more remarkable.

SUMMARY OF THE INVENTION

[0007] The object of the present invention is to provide a novelthermoplastic styrenic resin which is excellent in fluidity and vacuumformability along with excellent appearance of color on processing.

[0008] The present invention therefore provides a thermoplastic styrenicresin composition which comprises a styrenic copolymer (A) comprising15-100 parts by weight of a unit derived from a styrenic monomer (i-1),0-45 parts by weight of a unit derived from a vinyl cyanide monomer(i-2), 0-40 parts by weight of a unit derived from a copolymerizablevinyl monomer (i-3) other than above monomer, and 0.0005-1.0 parts byweight of a unit derived from a polyfunctional maleimide monomer, allbased on 100 parts by weight of the total amount of (i-1) to (i-3)

[0009] The present invention further provides a rubber modifiedthermoplastic styrenic resin composition which comprises of a styreniccopolymer (A) as the continuous phase comprising 15-100 parts by weightof a unit derived from a styrenic monomer (i-1), 0-45 parts by weight ofa unit derived from a vinyl cyanide monomer (i-2), 0-40 parts by weightof a unit derived from a copolymerizable vinyl monomer (i-3) other thanthe above monomers, and 0.0005-1.0 parts by weight of a unit derivedfrom a polyfunctional maleimide monomer, all based on 100 parts byweight of the total amount of (i-1) to (i-3), and rubber particle (B) asthe dispersed phase, wherein the rubber content of the rubber modifiedthermoplastic styrenic resin composition is in the range of 1-40 weight%.

[0010] The rubber modified thermoplastic styrenic resin composition thusobtained has excellent heat stability, impact strength, fluidity,thickness uniformity after vacuum forming process, and good uniformityof glass of the injection product after painting.

BRIEF DESCRIPTION OF THE DRAWING

[0011]FIG. 1 is a layout of the instrument for maximum extension stressanalysis in the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0012] Examples of styrenic monomer (i-1) used in the present inventionare styrene, α-methylstyrene, p-tertiary butylstyrene, p-methylstyrene,o-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene,α-methyl-p-methyl styrene or bromostyrene, etc. Among these, styrene orα-methylstyrene is preferred. They may be used either singly or incombination. The amount of styrenic monomer (i-1) used in the presentinvention is 15-100 parts by weight, preferably 20-95 parts by weight,and most preferably 25-90 parts by weight.

[0013] Examples of the vinyl cyanide monomer (i-2) used in the presentinvention are acrylonitrile, α-methylacrylonitrile, etc. Among these,acrylonitrile is preferred. The amount of vinyl cyanide monomer (i-2)used in the present invention is 0-45 parts by weight, preferably 2-40parts by weight, most preferably 3-40 parts by weight.

[0014] The copolymerizable vinyl monomer (i-3) which is copolymerizablewith styrenic monomer (i-1) may be ester of acrylic acid, ester ofmethacrylic acid and monofunctional maleimide monomer, etc.

[0015] Examples of ester of acrylic acid are methyl acrylate, ethylacrylate, iso-propyl acrylate, butyl acrylate, polyethylene glycoldiacrylate, etc. Among these, butyl acrylate is preferred.

[0016] Examples of methacrylic acid are methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, benzylmethacrylate, hexyl methacrylate, cyclohexyl methacrylate, dodecylmethacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate,dimethyl aminoethyl methacrylate, ethylene dimethacrylate, neopentyldimethactylate, etc. Among these, methyl methacrylate or butylmethacrylate is preferred.

[0017] Monofunctional maleimide monomer means that the monomer containsonly one functional group of maleimide. Examples of monofunctionalmaleimide monomer are maleimide, N-methyl maleimide, N-iso-propylmaleimide, N-butyl maleimide, N-hexyl maleimide, N-octyl maleimide,N-dodecyl maleimide, N-cyclohexyl maleimide, N-phenyl maleimide.N-2-methyl maleimide, N-2,3-dimethyl phenyl maleimide, N-2,4-dimethylphenyl maleimide, N-2,3-diethyl phenyl maleimide, N-2,4-diethyl phenylmaleimide, N-2,3-dibutyl phenyl maleimide, N-2,4-dibutyl phenylmaleimide, N-2,6-dimethyl phenyl maleimide, N-2,3-dichlorophenylmaleimide, N-2,4-dichlorophenyl maleimide, N-2,3-dibromophenyl maleimideor N-2,4-dibromophenyl maleimide, etc. Among these, N-phenyl maleimideis preferred.

[0018] Furthermore, the copolymerizable vinyl monomer (i-3) may also beother ethylenic vinyl monomer, such as, acrylic acid, methacrylic acid,maleic anhydride, methyl maleic anhydride, fumaric acid, itaconic acidand their ester (for example, dimethyl fumarate, dibutyl itaconate),ethylene, propylene, 1-butylene, 1-pentene, 4-methyl-1-pentene, ethylenechloride, vinylidene chloride, tetrafluoroethylene,chlorotrifluoroethylene, hexafluoropropylene, butadiene, propenyl amine,iso-butenyl amine, vinyl acetate, ethyl vinyl ether, methyl vinylketone, triallyl isocyanate, etc.

[0019] The amount of the copolymerizable vinyl monomer (i-3) in thepresent invention is 0-40 parts by weight, preferably 2-40 parts byweight, and most preferably 3-38 parts by weight. Among thesecopolymerizable vinyl monomer (i-3), ester of acrylic acid, ester ofmethacrylic acid or monofunctional maleimide monomer is preferred.

[0020] The polyfunctional maleimide monomer used in the presentinvention means that the monomer contains at least 2 functional group ofmaleimide, for example, 2, 3, or 4 functional groups of maleimide,wherein bismaleimide monomer is preferred. The structure of saidbismaleimide is as follows:

[0021] [wherein, X is alkylene of 1-10 carbon atoms, arylene, carbonylgroup, —SO₂—, —SO—, —O—, —O—R—O— (R may be alkylene or arylene)]

[0022] Examples of bismaleimide are N,N′-4,4′-(3,3′-dimethyl diphenylmethane) bismaleimide, N,N′-4,4′-(3,3′-diethyl diphenyl methane)bismaleimide, N,N′-4,4′-diphenyl methane bismaleimide,N,N′-4,4′-2,2′-diphenyl propane bismaleimide, N,N′-4,4′-diphenyl etherbismaleimide, N,N′-3,3′-diphenyl sulfone bismaleimide,N,N′-4,4′-diphenyl sulfone bismaleimide, N,N′-4,4′-diphenyl sulfoxidebismaleimide, N,N′-4,4′-benzophenone bismaleimide, N,N′-1,3′-phenylenedimaleimide, wherein, N,N′-4,4′-diphenyl methane bismaleimide andN,N′-1,3-phenylene dimaleimide are preferred.

[0023] The amount of polyfunctional maleimide used in the presentinvention is 0.0005-1.0 parts by weight, preferably 0.001-0.3 parts byweight, most preferably 0.003-0.1 parts by weight.

[0024] The thermoplastic styrenic resin composition of the presentinvention comprises styrenic copolymer (A) which is comprising 15-100parts by weight of a unit derived from a styrene monomer (i-1), 0-45parts by weight of a unit derived from a vinyl cyanide monomer (i-2),0-40 parts by weight of a unit derived from a copolymerizable vinylmonomer (i-3) other than the above monomer, and 0.0005-1.0 parts byweight of a unit derived from a polyfunctional maleimide monomer, allbased on 100 parts by weight of the total amount of (i-1) to (i-3). Whenthe amount of unit derived from a polyfunctional maleimide monomer inthe styrenic copolymer (A) is greater than 0.0005 parts by weight, thethermoplastic styrenic resin composition is excellent in maximumextension stress during forming process. When the amount of unit derivedfrom a polyfunctional maleimide monomer is less than 1.0 part by weight,the thermoplastic styrenic resin composition is excellent in fluidityand color.

[0025] In the thermoplastic styrenic resin composition of the presentinvention, the amount of residual polyfunctional maleimide monomer isless than 100 ppm, preferably less than 60 ppm, most preferably lessthan 30 ppm. It is the best to get the thermoplastic styrenic resincomposition without any residual polyfunctional maleimide monomer. Forthe analysis of residual monomer, the thermoplastic styrenic resincomposition should be dissolved in THF, the solution is then analyzed by6890A Gas Chromatography with flame ionization detector manufacturedfrom Hewlett Packard company. The obtained value is in the unit of PPM,which is based on 100 weight % of the thermoplastic styrenic resincomposition.

[0026] In the thermoplastic styrenic resin composition of the presentinvention, if the amount of residual polyfunctional maleimide monomer isless than 100 ppm, a better color will be obtained.

[0027] In the styrenic copolymer (A) of the present invention, the ratioof MZ (Z-average molecular weight)/Mw (weight-average molecular weight)is in the range of 2-8, preferably 2.5-7, most preferably 3-6. It isanalyzed by gel permeation chromatography (GPC) manufactured from WatersCompany with differential refractometer detection and light scatteringdetection. When the ratio of MZ/MW of styrenic copolymer (A) is between2 and 8, the thermoplastic styrenic resin composition or the rubbermodified thermoplastic styrenic resin composition is excellent influidity, maximum extension stress and color.

[0028] In the thermoplastic styrenic resin composition of the presentinvention, the $\begin{matrix}{{g\quad M} = \frac{\left( r^{2} \right)_{b}}{\left( r^{2} \right)_{l}}} & {{formula}\quad (2)}\end{matrix}$

[0029] branching ratio (gM) is in the range of 0.45-0.95, which could becalculated according to following equation:

[0030] (r²)_(b): the rotating radius of branching molecule

[0031] (r²)_(l): the rotating radius of linear molecule

[0032] The analysis of branching ratio (gM) could be analyzed by acombination of GPC and Minidawn type MALLS. The GPC is manufactured byWaters Company and the Minidawn type Multi-angle Laser Light Scattering(MALLS) is manufactured by Wyatt Technology Corporation, to obtain therotating radius of branching molecule and linear molecule at a molarmass of 1×10⁶ g/mole, and then it can be calculated according to theabove-mentioned equation.

[0033] Branching ratio is an index representing branching structure ofthe polymer. For the polymer with the same molecular weight, the smallerthe value of the branching ratio is, the higher branching structure itwill be. The desired gM can be obtained by adjusting the dosage ofpolyfunctional maleimide monomer. If the amount of maleimide monomerused is controlled in the range suggested in the present invention, thegM will be easily achieved.

[0034] In this thermoplastic styrenic resin composition of the presentinvention, the branching ratio (gM) is in the range of 0.45-0.95,preferably 0.5-0.9, most preferably 0.6-0.8. When the gM value is in therange of 0.45-0.95, the thermoplastic styrenic resin composition hasbetter fluidity, maximum extension stress and color.

[0035] Generally, the styrenic copolymer (A) could be prepared bycontinuous bulk or solution polymerization, emulsion polymerization orsuspension polymerization. Among these, continuous bulk or solutionpolymerization is especially better. The reactor for the above-mentionedpolymerization may be plug flow reactor (PFR), continuous stirred tankreactor (CSTR) or static mixer reactor, etc. Among these, the CSTR ispreferred. The reactors used could be only one kind of the above or acombination of the above. The number of reactors used can be 1, 2, 3, orgreater than 3. When more than 2 reactors are used, the final reactor isbetter to be PFR. During preparation of the styrenic copolymer (A) ofthe present invention, the raw material solution is continuouslyintroduced into the reactor for polymerization. It is better to add theinitiator during polymerization.

[0036] In the preparation of the styrenic copolymer (A) of the presentinvention, the amount of the initiator is in the range of 0-1 parts byweight, preferably 0.001-0.5 parts by weight. Examples of the initiatorused in the present invention are monofunctional and polyfunctionalinitiators. Examples of the monofunctional initiator are benzoylperoxide, dicumyl peroxide, t-butyl peroxide, t-butyl hydroperoxide,cumene hydroperoxide, t-butyl-peroxy benzoate, bis-2-ethylhexyl peroxydicarbonate, tert-butyl peroxy isopropyl carbonate (hereinafterabbreviated as BPIC), cyclohexanone peroxy,2,2′-azo-bis-isobutyronitrile, 1,1′-azo-bis-(cyclohexane-1-carbonitrile,2,2′-azo-bis-2-methyl butyronitrile. etc. Among these, benzoyl peroxideand dicumyl peroxide are preferred.

[0037] Examples of the polyfunctional initiator are 1,1-bis-(t-butylperoxy)cyclohexane, (hereinafter abbreviated as TX-22),1,1′-bis-(t-butylperoxy)-3,3,5-trimethyl cyclohexane, (hereinafterabbreviated as TX-29A), 2,5-dimethyl-2,5-bis-(2-ethylhexanoxyperoxy)hexane. 4-(t-butyl peroxy carbonyl)-3-hexyl-6-[7-(t-butyl peroxycarbonyl) heptyl]cyclohexane, di-t-butyl-diperoxyazelate,2,5-dimethyl-2,5-bis-(benzoyl peroxy) hexane, di-t-butylperoxy-hexahydro-terephthalate(hereinafter abbreviated as BPHTH),2,2-bis-(4,4-di-t-butyl peroxy)cyclohexyl propane, polyfunctionalmonoperoxycarbonate (for example, Luperox JWE made by ATOFINA inAmerica). Among these, TX-29A or BPHTP is preferred.

[0038] The polymerization temperature is controlled in the range of20-300° C., preferably 60-250° C., and most preferably 80-200° C. Thepolymerization pressure of the reactor is controlled in the range of1-10 kg/cm². The residence time of raw material solution in reactors isusually in the range of 0.5-15 hours, preferably 1-10 hours. In thepresent invention, chain transfer agents could be used to controlmolecular weight, which amount is usually in the range of 0-2 parts byweight, preferably 0.001-1 parts by weight. The chain transfer agent canbe monofunctional or polyfunctional chain transfer agent. Examples ofmonofunctional chain transfer agent are:

[0039] 1. mercaptan: methyl mercaptan, n-butyl mercaptan, cyclohexylmercaptan, n-dodecyl mercaptan, stearyl mercaptan (hereinafterabbreviated as TDM), n-propyl mercaptan, n-octyl mercaptan, t-octylmercaptan, t-nonyl mercaptan, etc.

[0040] 2. alkyl amine: monoethylamine, dimethylamine, triethylamine,isopropylamine, diisopropylamine, butylamine, di-n-butylamine,tri-n-butylamine, etc.

[0041] 3. others: pentaphenylethane, α-methyl styrene dimmer,terpinolene.

[0042] Among these, n-dodecyl mercaptan and t-dodecyl mercaptan arepreferred.

[0043] Examples of polyfunctional chain transfer agent arepentaerythritol tetrakis (3-mercapto propionate), pentaerythritoltetrakis (2-mercapto acetate), trimethylolpropane tris (2-mercaptoacetate), trimethylolpropane tris (3-mercapto propionate)(hereinafterabbreviated as TMPT), trimethylol-propane tris (6-mercapto hexanate),etc. Among these, trimethylolpropane tris (3-mercapto propionate) ispreferred.

[0044] The styrenic copolymer (A) of the present invention is preparedby continuous introduction of raw material solution into the reactor forpolymerization. When the monomers in the raw material solution attainthe desired conversions, the polymer solution is then continuouslyintroduced into devolatilization equipment for removing of unreactedmonomers and other volatiles. Usually, the devolatilization equipmentused could be reduced pressure devolatilization tank or extrusiondevolatilization equipment. The unreacted monomers and volatiles couldbe recovered in condenser, which could be reused as raw materialsolution after dehydration, if necessary.

[0045] For the preparation of the styrenic monomer (A) of the presentinvention, the raw material solution comprising 15-100 parts by weightof the styrenic monomer (i-1), 0-45 parts by weight of the vinyl cyanidemonomer (i-2), 0-40 parts by weight of the copolymerizable vinyl monomer(i-3), 0.0005-1.0 parts by weight of the polyfunctional maleimidemonomer, and 0-60 parts by weight of solvent is used, all based on 100parts by weight of the total amount of (i-1) to (i-3). Among these, theamount of styrenic monomer (i-1) is preferably 20-95 parts by weight,most preferably 25-90 parts by weight. The amount of vinyl cyanide (i-2)is preferably 2-40 parts by weight, most preferably 3-38 parts byweight. The amount of polyfunctional maleimide is preferably 0.001-0.3parts by weight, most preferably 0.003-0.1 parts by weight.

[0046] In the raw material solution used of the present invention,examples of the styrenic monomer, vinyl cyanide monomer, copolymerizablevinyl monomer, and polyfunctional maleimide monomer are described thesame as mentioned above, which will not be repeated here. Wherein, thecopolymerizable vinyl monomer is preferably selected from ester ofacrylic acid, ester of methacrylic acid and monofunctional maleimidemonomer, and the amount of the copolymerizable vinyl monomer is 0-40parts by weight, preferably 2-40 weight parts, most preferably 3-38parts by weight.

[0047] Examples of the solvent used for raw material solution arebenzene, toluene, ethylbenzene, p-dimethylbenzene, o-dimethylbenzene,m-dimethylbenzene, pentane, octane, cyclohexane, methyl ethyl ketone,acetone, methyl butyl ketone, etc.

[0048] In the present invention, the styrenic copolymer (A) used as thecontinuous phase and rubber particle (B) used as the dispersed phaseform the rubber modified thermoplastic styrenic resin composition, inwhich the rubber content is in the range of 1-40 weight %, preferably3-35 weight %.

[0049] The rubber modified thermoplastic styrenic resin composition canalso be manufactured by addition of rubber into raw material solutionduring the polymerization of the styrenic copolymer (A) (hereinafterreferred to as simultaneous grafting method) or by blending andextrusion of the rubber (for example, rubber or rubber graft copolymer,wherein rubber graft copolymer is preferred) with the styrenic copolymer(A) of the present invention (hereinafter referred to as mixing method).The simultaneous grafting method could usually be conducted by bulkpolymerization, solution polymerization, emulsion polymerization orsuspension polymerization. The rubber graft copolymer could usually beobtained by emulsion polymerization or emulsion-bulk polymerization;especially emulsion polymerization is preferred.

[0050] In the rubber modified thermoplastic styrenic resin compositionof the present invention, the weight-average diameter of rubber particle(B) is usually in the range of 0.05-10 μm, preferably 0.1-5 μm, mostpreferably 0.1-1 μm.

[0051] The preparation of rubber modified thermoplastic styrenic resincomposition of the present invention is described as following:

Method 1: Simultaneous Grafting Method

[0052] Method 1 could be used to manufacture rubber modifiedthermoplastic styrenic resin composition. It is preferable to usecontinuous bulk or solution polymerization for Method 1. The reactorsused in Method 1 include plug flow reactor (PFR), continuous stirredtank reactor (CSTR), static mixer reactor, etc., wherein CSTR ispreferred. The reactors used could be single or a combination of two ormore. If two or more reactors are used, the final reactor is preferablyPFR. The raw material solution required for the rubber modifiedthermoplastic styrenic resin composition (containing rubber) iscontinuously introduced into the reactor for polymerization at first.The polymerization temperature is controlled between 30-300° C.,preferably 60-250° C., most preferably 80-200° C. Polymerizationpressure is controlled between 1-10 kg/cm². The residence time in thereactor is 0.5-15 hours, preferably 1-10 hours. For the controlling ofmolecular weight, initiators and chain transfer agents can be used inthe preparation of rubber modified thermoplastic styrenic resincomposition, if necessary.

[0053] The rubber modified thermoplastic styrenic resin composition isprepared by continuously introducing the raw material solution into thereactor for polymerization. When all the monomers in the raw materialsolution attain desired conversions, the polymer solution is thencontinuously introduced into devolatilization equipment for removing ofunreacted monomers and other volatiles. Usually, the devolatilizationequipment used can be reduced pressure devolatilization tank orextrusion devolatilization equipment. The unreacted monomers andvolatiles could be recovered in condenser, which could be reused as rawmaterial solution after dehydration, if necessary.

[0054] For the preparation of the rubber modified thermoplastic styrenicresin composition of the present invention, the raw material solution inbulk or solution polymerization comprises 15-100 parts by weight of thestyrenic monomer (i-1), 0-45 parts by weight of the vinyl cyanidemonomer (i-2), 0-40 parts by weight of the copolymerizable vinyl monomer(i-3) other than the above monomer, 0.0005-1.0 parts by weight of thepolyfunctional maleimide monomer, 0-60 parts by weight of the solventand 0.5-25 parts by weight of the rubber, all based on 100 parts byweight of the total amount of (i-1) to (i-3). Among these, the styrenicmonomer, vinyl cyanide monomer, copolymerizable vinyl monomer, solvent,and optionally initiator or chains transfer agent are described the sameas above-mentioned, so they are not repeated here.

[0055] In Method 1, the rubber modified thermoplastic styrenic resincomposition may also be prepared by emulsion polymerization, which issimilar to the preparation of the rubber graft copolymer (B′) which willbe mentioned later except that 0.0005˜1.0 wt % (based on 100 wt %monomer mixture) of polyfunctional maleimide monomer is additionallyadded.

[0056] In the initial stage of the bulk or solution polymerization forthe rubber modified thermoplastic styrenic resin composition, the rawmaterial solution contains rubber, styrenic monomer, vinyl cyanidemonomer, etc., wherein the rubber phase exists in a continuous phase.The conversion of the monomers such as styrenic monomer, vinyl cyanidemonomer, etc., is increased gradually along with graft polymerization.Under the action of stirring and higher conversion, the rubber will begradually surrounded by styrenic monomer, vinyl cyanide monomer andpolymer which is polymerized from above monomers, etc., and as a resultthe rubber phase is converted into separated particle (dispersed phase).In another respect the mixture of styrenic monomer, vinyl cyanidemonomer, etc., and their polymer, which originally exist indiscontinuous phase, is converted into continuous phase. Finally, therubber particle phase is formed. The weight-average diameter of rubberparticle is in the range of 0.05-10 μm, preferably 0.1-5 μm, mostpreferably 0.1-1 μm.

[0057] Examples of the rubber used in Method I are diene rubber,polyolefin rubber (for example, ethylene-propylene rubber), polyacrylaterubber, polysiloxane rubber and others. The diene rubber is the polymerwhich is polymerized from diene monomer, and the glass temperature isless than 0° C. Examples of the diene rubber are butadiene rubber,isoprene rubber, chlorobutadiene rubber, EPDM rubber, styrene-dienerubber, acrylonitrile-diene rubber. Among these, the butadiene rubberincludes Hi-Cis content butadiene rubber and Low-Cis content butadienerubber. In Hi-Cis content butadiene rubber, the typical ratio ofCis/vinyl by weight is (94-99%)/(0-5%), and the other is TransStructure. The Mooney viscosity is in the range of 20-120 and themolecular weight is in the range of 100000-800000. In Low-Cis contentbutadiene rubber, the typical ratio of Cis/vinyl by weight is in therange of (20-40%)/(6-20%), and the other is Trans Structure. The Mooneyviscosity is in the range of 20-120 and the molecular weight is in therange of 100000-800000. Styrene-diene rubber includes styrene-butadienerubber, Styrene-isoprene rubber, etc., which could be random copolymeror taper copolymer, in which, the styrene content in thestyrene-butadiene rubber is less than 50 weight % and the molecularweight is 50000-600000. Among these, the butadiene rubber andstyrene-butadiene rubber is preferred.

Method 2: Mixing Method

[0058] According to Method 2, the rubber modified thermoplastic styrenicresin composition of the present invention could be prepared by mixingof styrenic copolymer (A) with rubber graft copolymer (B′) and then theabove mixture is extruded.

[0059] Method 2 could be conducted by dry-mixing of styrenic copolymer(A) with rubber graft copolymer (B′) in an conventional Henschel mixerand then the above mixture is extruded by extruder such as single,twin-screw extruder, Banbury mixer and Brabender plastificator. Afterextrusion, the resulting resin is cooled and palletized.

[0060] Rubber graft copolymer (B′) could be prepared by bulk or solutionpolymerization, emulsion polymerization or suspension polymerization. Inthe preparation by bulk or solution polymerization, the rubber graftcopolymer (B′) will be obtained by the graft polymerization of the rawmaterial solution, which contains 15-100 parts by weight of the styrenicmonomer (i-1), 0-45 parts by weight of the vinyl cyanide monomer (i-2),0-40 parts by weight of the copolymerizable vinyl monomer (i-3), 0-60parts by weight of the solvent and 0.5-2.5 parts by weight of therubber, all based on 100 parts by weight of the total amount of (i-1) to(i-3). Usually the raw material solution contains no polyfunctionalmaleimide monomer. If polyfunctional maleimide is used, the amount ofthe polyfunctional maleimide should be below the lower limit stipulatedin the present invention. The examples of the rubber are similar to thatdescribed in Method 1.

[0061] In the initial stage of the bulk or solution polymerization forthe rubber graft copolymer (B′), the raw material solution containsstyrenic monomer, vinyl cyanide monomer and rubber, etc., and the rubberphase exists in a continuous phase. The conversion of the monomers suchas styrenic monomer, vinyl cyanide monomer, etc., is increased graduallyalong with graft polymerization. Under the action of stirring and higherconversion, the rubber will be gradually surrounded by styrenic monomer,vinyl cyanide monomer and polymer which is polymerized from abovemonomers, etc., and as a result the rubber phase is converted intoseparated particle (dispersed phase). In another respect, the mixture ofstyrenic monomer, vinyl cyanide monomer, etc., and their polymer whichoriginally exist in discontinuous phase is converted into continuousphase. Finally, the rubber particle phase is formed. The weight-averagediameter of rubber particle is in the range of 0.05-10 μm, preferably,0.1-5 μm most preferably 0.1-1 μm.

[0062] The preparation of rubber graft copolymer (B′) could also beconducted by emulsion polymerization which contains a mixture of 40-90parts by weight of the rubber latex (solid content) and 60-10 parts byweight of the monomer mixture comprising styrenic monomer 15-100 weight%, vinyl cyanide monomer 0-45 weight %, and the other copolymerizablevinyl monomer 0-40 weight %. The initiator and chain transfer agent canalso be added during emulsion polymerization, if necessary. The abovemixture is polymerized to form rubber graft copolymer emulsion at first,then the rubber graft copolymer emulsion is coagulated, dehydrated, anddried to produce the rubber graft copolymer (B′) required in the presentinvention.

[0063] The composition of the rubber latex is similar to that describedin Method 1, wherein, the diene rubber is preferred. The diene rubberlatex could be prepared by emulsion polymerization from diene monomer(for example, butadiene) or 100-50 parts by weight of the diene monomerwith 0-50 parts by weight of the other copolymerizable vinyl monomerssuch as styrene, acrylonitrile, ester of (meth)acrylic acid. Theweight-average diameter of rubber particle is in the range of 0.05-0.6μm. The diene rubber latex could also be prepared by emulsionpolymerization from the above monomers, with rubber particle size ofweight-average diameter of 0.05-0.2 μm, firstly. Then, the diene rubberlatex is agglomerated to enlarge the rubber particle size having aweight average diameter of 0.22-0.6 μm by a conventional rubberagglomerating method. Examples of the rubber agglomerating method arefreezing agglomerating, a mechanical stirring agglomerating and achemical agglomerating method. The chemical agglomerating method isachieved by adding an additive such as acetic anhydride, hydrogenchloride, sulfuric acid, sodium chloride, potassium chloride, calciumchloride, (meth)acrylic acid—meth)acrylate copolymer (for example,methacrylic acid—butyl acrylate copolymer, methacrylic acid-ethylacrylate copolymer) and other polymeric agglomerating agent containing acarboxylic group.

[0064] In the present invention, the rubber content of the rubbermodified thermoplastic styrenic resin composition is in the range of1-40 weight %, preferably 4-35 weight %, most preferably 6-30 weight %.When the rubber content is in the range of 1-40 weight %, the rubbermodified thermoplastic styrenic resin composition is excellent in impactstrength, fluidity and other mechanical properties.

[0065] In the rubber modified thermoplastic styrenic resin compositionof the present invention, the residual polyfunctional maleimide monomeris less than 100 ppm, preferably below 60 ppm, most preferably below 30ppm. It is the best to get the rubber modified thermoplastic styrenicresin composition without any residual polyfunctional maleimide monomer.If the residual polyfunctional maleimide monomer is less than 100 ppm,the rubber modified thermoplastic styrenic resin composition isexcellent in heat stability and contaminations can be improved.

[0066] The branching ratio (gM) of the rubber modified thermoplasticstyrenic resin composition in this present invention is in the range of0.45-0.95, preferably 0.5-0.9, most preferably 0.6-0.8. If the branchingratio (gM) is in the range of 0.45-0.95, the rubber modifiedthermoplastic styrenic resin composition is excellent in fluidity andcolor. The analysis of gM is similar to that described above. But therubber particle of dispersed phase should be removed from the rubbermodified thermoplastic styrenic resin composition before analysis. Forexample, when determining the gM of rubber modified thermoplasticstyrenic resin composition prepared with simultaneous grafting, thesolvent, such as methyl ethyl ketone which can dissolve styreniccopolymer (A) but can not dissolve the rubber particle, should beselected at first. After that, the rubber particle could be removed byfiltration. The solvent could then be evaporated to obtain theingredient without rubber particle for analysis. Furthermore, when therubber modified thermoplastic styrenic resin composition is determinedfor MZ or MW, the styrenic copolymer (A) which contains no rubberparticle is also required.

[0067] In the rubber modified thermoplastic styrenic resin compositionof the present invention, the amount of unit derived from apolyfunctional maleimide monomer in styrenic copolymer (A) is in therange of 0.0005-1.0 parts by weight, preferably 0.001-0.3 parts byweight, most preferably 0.003-0.1 parts by weight. When the amount ofunit derived from a polyfunctional maleimide monomer in styreniccopolymer (A) is great than 0.0005 parts by weight, the rubber modifiedthermoplastic styrenic resin composition, especially used as the rawmaterial of thermoplastic processing, is excellent in thicknessuniformity after vacuum forming process and the gloss on the surface ofinjected products after painting process is also good. When the amountof unit derived from a polyfunctional maleimide monomer in styreniccopolymer (A) is less than 1.0 parts by weight, the rubber modifiedthermoplastic styrenic resin composition, especially used as the rawmaterial of thermoplastic processing is excellent in heat stability, andthe contaminations can be improved, and the gloss on the surface ofinjected products after painting process is also good. In addition, thepolymer is excellent in fluidity and the continuous polymerization couldbe proceeded smoothly.

[0068] The thermoplastic styrenic resin composition or the rubbermodified thermoplastic styrenic resin composition in this presentinvention, if necessary, could be added with various types of additivessuch as anti-oxidant, lubricant, UV-absorbent, UV-stabilizer,anti-static agent, colorant, etc. The additives could be added duringthe period of polymerization of styrenic copolymer (A) or extrusion ofthe thermoplastic styrenic resin composition. The amount of additives isless than 6 parts by weight, based on 100 parts by weight of thethermoplastic styrenic resin composition. Other additives such as fireretardant, impact modifier, etc. could also be used, if necessary. Theamount of other additives is less than 30 parts by weight, based on 100parts by weight of the thermoplastic styrenic resin composition.

[0069] If necessary, the thermoplastic styrenic resin composition orrubber modified thermoplastic styrenic resin composition of the presentinvention could be mixed with the resin other than thermoplasticstyrenic copolymer (A). Examples of the resin areacrylonitrile-butadiene-styrene resin, styrene-acrylonitrile resin,acrylonitrile-butadiene-α-methylstyrene resin,acrylonitrile-styrene-methyl methacrylate resin,acrylonitrile-styrene-N-phenyl maleimide resin, styrene-maleic anhydrideresin, styrene-N-phenyl maleimide resin, poly methyl methacrylate,polycarbonate resin, styrene-methacrylate resin,methacrylate-butadiene-styrene resin, polyamide resin, polyester resin,polyphenylene oxide resin, acrylonitrile-acrylate rubber-styrene resin,acrylonitrile-(ethylene-propylene rubber)-styrene resin, andacrylonitrile-silicon rubber-styrene resin, etc. They may be used eithersingly or in combination. The amount of the above resin is less than 80parts by weight, based on 100 parts by weight of the thermoplasticstyrenic resin composition or rubber modified thermoplastic styrenicresin composition.

EXAMPLE 1 Preparation of Styrenic Copolymer (A-1)

[0070] A mixture of 68 parts by weight of the styrene monomer, 32 partsby weight of the acrylonitrile, 0.02 parts by weight of theN,N′-4,4′-diphenyl methane bismaleimide, 20 parts by weight of theethylbenzene, 0.02 parts by weight of the initiator benzoyl peroxide and0.2 parts by weight of the chain transfer agent t-dodecyl mercaptan areprepared and then are continuously charged to two continuous stirredtank reactors in series, the volumes of reactors are 40 liters and 70liters respectively. The temperature of these two reactors arecontrolled at 100° C. and 120° C. respectively under the same pressureof 4 kg/cm². The total residence time in reactors is set for 2 hourswith the conversions in two reactors of 30 weight % and 50 weight %,respectively. After polymerization, the copolymer solution is introducedinto devolatilization equipment for removing of unreacted monomers andother volatiles. Usually, the devolatilization equipment could be usedincluding reduced pressure devolatilization tank or extrusiondevolatilization equipment. Then the melted polymer is extruded. Afterextrusion, the resulting resin is cooled and palletized, and thestyrenic copolymer (A-1) of the present invention is obtained. Thepreparation of the styrenic copolymer (A-1) and physical properties areshown in Table 1.

EXAMPLE 2 Preparation of Styrenic Copolymer (A-2)

[0071] The procedures of Example 1 is repeated except that the amount ofN,N′-4,4′-diphenyl methane bismaleimide is changed to 0.01 parts byweight, and the preparation and physical properties of the styreniccopolymer (A-2) are shown in Table 1.

EXAMPLE 3 Preparation of Styrenic Copolymer (A-3)

[0072] The procedures of Example 1 is repeated except that the amount ofmonomers and initiators are changed. That is, 58 parts by weight of thestyrene monomer, 22 parts by weight of the acrylonitrile, 0.01 parts byweight of the N,N′-4,4′-diphenyl methane bismaleimide and 20 parts byweight of the N-phenyl maleimide, and the initiator 0.015 parts byweight of the benzoyl peroxide and 0.005 parts by weight of the TX-29Aare used. The preparation of the styrenic copolymer (A-3) and physicalproperties are shown in Table 1.

EXAMPLE 4 Preparation of Styrenic Copolymer (A-4)

[0073] A mixture of 100 parts by weight of the styrene monomer, 0.02parts by weight of the N,N′-4,4′-diphenyl methane bismaleimide, 8 partsby weight of the ethylbenzene, 0.02 part by weight of the initiatorbenzoyl peroxide, 0.02 part by weight of the chain transfer agentt-dodecyl mercaptan are prepared and then are continuously charged tothree plug flow reactors in series, which have a same volume of 100liters and are controlled at 110° C., 130° C. and 160° C. respectivelywith a same pressure of 3 kg/cm², the total residence time in reactorsis set for 7 hours, the conversion of monomers in 3 reactors are kept at30 weight %, 60 weight %, 85 weight % respectively. Afterpolymerization, the copolymer solution is usually introduced intodevolatilization equipment for removing of unreacted monomers and othervolatiles. Usually, the devolatilization equipment could be usedincluding reduced pressure devolatilization tank or extrusiondevolatilization equipment. Then the melted polymer is extruded. Afterextrusion, the resulting resin is cooled and palletized, and thestyrenic copolymer (A-4) of the present invention is obtained. Thepreparation of the styrenic copolymer (A-4) and physical properties areshown in Table 1.

COMPARATIVE EXAMPLE 1 Preparation of Styrenic Copolymer (A-5)

[0074] The procedure of Example 1 is repeated except thatN,N′-4,4′-diphenyl methane bismaleimide monomer is not used, thepreparation and physical properties of the styrenic copolymer (A-5) areshown in Table 1.

COMPARATIVE EXAMPLE 2 Preparation of Styrenic Copolymer (A-5)

[0075] The procedure of Example I is repeated except that the amount ofN,N′-4,4′-diphenyl methane bismaleimide is changed to 1.5 parts byweight, during polymerization, the viscosity of the reaction system isincreased sharply, the color of the product is bad and thecontaminations are increased, the reaction could not be continued atlast.

EXAMPLE 5 Preparation of Rubber Modified Thermoplastic Styrenic ResinComposition (A-5)

[0076] A mixture of 74 parts by weight of the styrene monomer, 26 partsby weight of the acrylonitrile, 12 parts by weight of the butadienerubber, 0.02 part by weight of the N,N′-4,4′-diphenyl methanebismaleimide, 20 parts by weight of the ethylbenzene, 0.05 part byweight of the initiator benzoyl peroxide, and 0.3 part by weight of thechain transfer agent t-dodecyl mercaptan are prepared and then arecontinuously introduced into four continuous stirred tank reactors inseries, which are the same volume of 45 liters. The polymerizationtemperature are controlled at 95° C., 100° C. and 110° C. and 120° C.,respectively, with the pressure of 4.5 kg/cm², 4 kg/cm², 4 kg/cm² and 4kg/cm², respectively. The total residence time in reactors is set for 4hours. The monomer conversion in 4 reactors is kept at 22 weight %, 31weight %, 45 weight % and 52 weight %, respectively.

[0077] After polymerization, the copolymer solution is usuallyintroduced into devolatilization equipment for removing of unreactedmonomers and other volatiles. Usually, the devolatilization equipmentcould be used including reduced pressure devolatilization tank orextrusion devolatilization equipment. Then the melted polymer isextruded, after extrusion, the resulting resin is cooled and palletized,and the rubber modified thermoplastic styrenic copolymer (C-1) of thepresent invention is obtained. The rubber modified thermoplasticstyrenic copolymer (C-1) comprises styrenic copolymer (A) as thecontinuous phase, which containing units of styrene monomer, vinylcyanide, etc. and rubber particle (B) as the dispersed phase. Theweight-average diameter of rubber particle (B) is 0.81 μm. Thepreparation of the rubber modified styrenic resin composition (C-1) andphysical properties are shown in Table 2.

COMPARATIVE EXAMPLE 3 Preparation of Rubber Modified ThermoplasticStyrenic Resin Composition (C-2)

[0078] The procedure of Example 5 is repeated except thatN,N′-4,4′-diphenyl methane bismaleimide monomer is not used. Theweight-average diameter of rubber particle (B) is 0.81 μm. Thepreparation and physical properties of the rubber modified thermoplasticstyrenic resin composition (C-2) are shown in Table 2.

COMPARATIVE EXAMPLE 4 Preparation of Rubber Modified ThermoplasticStyrenic Resin Composition (C-3)

[0079] The procedure of Example 5 is repeated except that 0.02 parts byweight of N,N′-4,4′-diphenyl methane bismaleimide monomer is replacedwith 0.02 parts by weight of PGDA (Neopentyl glycol diacrylate). Thepreparation and physical properties of the rubber modified thermoplasticstyrenic resin composition (C-3) are shown in Table 2.

REFERENCE EXAMPLE 1 Preparation of Rubber Graft Copolymer (B′-1)

[0080] A mixture of 72 parts by weight of the styrene monomer, 28 partsby weight of the acrylonitrile, 20 parts by weight of the ethylbenzene,6.5 parts by weight of the butadiene rubber, 0.05 part by weight of theinitiator benzoyl peroxide, and 0.3 part by weight of the chain transferagent t-dodecyl mercaptan is prepared and then is continuouslyintroduced into four continuous stirred tank reactors in series, whichare the same volume of 45 liters. The polymerization temperature in thefour reactors are controlled at 90° C., 100° C., 110° C., and 120° C.respectively with a same pressure of 4 kg/cm², the monomer conversionsin the four reactors are controlled at 23 weight %, 35 weight %, 42weight %, and 51 weight % respectively.

[0081] After polymerization, the copolymer solution is introduced intodevolatilization equipment for removing of unreacted monomers and othervolatiles. Usually, the devolatilization equipment could be usedincluding reduced pressure devolatilization tank or extrusiondevolatilization equipment. Then the melted polymer is extruded. Afterextrusion, the resulting resin is cooled and palletized, and rubbergraft copolymer (B′-1) is obtained. In the rubber graft copolymer (B′-1)of the present invention, the rubber content is 10 weight % and theweight-average diameter is 0.79 μm.

REFERENCE EXAMPLE 2 Preparation of Rubber Graft Copolymer (B′-2)

[0082] TABLE 3 Parts by Composition weight 1,3-butadiene 150.0 PotassiumPersulfate Solution (1%) 15.0 Potassium Oleate 2.0 Distilled Water 190.0Ethylene Glycol dimethacrylate 0.13

[0083] A mixture based on the recipe given in Table 3 is polymerized at65° C. for 14 hours, and the rubber latex can be obtained. Theconversion is 94%, solid content is about 36 wt % and weight-averagediameter of the rubber particle is 0.1 μm.

[0084] In addition, a polymeric agglomerating agent containing acarboxylic group, is prepared in accordance with the recipe in Table 4.TABLE 4 Composition Parts by weight Butyl acrylate 90.0 Methacrylic acid10.0 Potassium Persulfate Solution (1%) 0.5 Sodium dodecyl sulfate (10%)0.5 n-dodecyl Mercaptan 1.0 Distilled Water 200.0

[0085] A mixture based on the recipe given in Table 4 is polymerized at75° C. for 5 hours, and the agglomerating agent can be obtained. Theconversion is 95% and the pH value is 6.0.

[0086] Then 100 parts by weight (dry) of the rubber latex areagglomerated with 3.0 parts by weight (dry) of polymeric agglomeratingagent containing a carboxylic group. And an agglomerated rubber latexwith a pH of 8.5 and weight average diameter of 0.31 μm can be obtained.

[0087] Finally, the agglomerated rubber latex is grafted withacrylonitrile and styrene in accordance with the recipe in Table 5 toachieve rubber graft copolymer (B′-2). TABLE 5 Composition Parts byweight agglomerated rubber latex (Dry 100.0 Weight) Styrene monomer 75.0Acrylonitrile 25.0 t-dodecyl Mercaptan 2.0 Cumene Hydroperoxide 3.0Ferrous Sulfate (0.2%) 3.0 Formaldehyde Sodium sulfoxylate 0.9 (10%)EDTA Solution (0.25%) 3.0

[0088] The rubber graft copolymer latex prepared from the abovecomponents are coagulated with calcium chloride, dehydrated, and driedto have a moisture content of below 2%, thus the powdery rubber graftcopolymer (B′-2) required in this invention could be obtained (RubberContent of 50 weight %, weight-average diameter of 0.3 1 μm).

EXAMPLE 6 Preparation of Rubber Modified Thermoplastic Styrenic ResinComposition (C4)

[0089] A mixture of 20 parts by weight of the rubber graft copolymer(B′-1), 30 parts by weight of the rubber graft copolymer (B′-2), 50parts by weight of the styrenic copolymer (A-1) and 0.3 parts by weightof the ethylene bisstearamide (EBS) are dry-blended by using a Henschelmixer to form a mixture. The mixture is fed into a twin-screw extruderwhich is provided with a barrel temperature kept at 200-220° C., a dietemperature kept at 220° C., and a vent hole, to produce the rubbermodified thermoplastic styrenic resin composition (C-4) in pellet form.The weight-average rubber particle diameter is 0.36 μm, and thepreparation and physical properties are shown in Table 6.

EXAMPLE 7 Preparation of Rubber Modified Thermoplastic Styrenic ResinComposition (C-5)

[0090] The procedure of Example 6 is repeated except that the styreniccopolymer (A-1) is replaced by styrenic copolymer (A-3), and thetemperature of the barrel and die of the extruder are controlled at220-240° C. and 240° C., respectively. The preparation of thethermoplastic styrenic resin composition (C-5) and physical propertiesare shown in Table 6.

EXAMPLE 8 Preparation of Rubber Modified Thermoplastic Styrenic ResinComposition (C-6)

[0091] A mixture of 36 parts by weight of the rubber graft copolymer(D-2), 64 parts by weight of the styrenic copolymer (A-1) and 0.3 partsby weight of the ethylene bisstearamide are dry-blended by using aHenschel mixer to form a mixture. The mixture is fed into a twin-screwextruder which is provided with a barrel temperature kept at 200-220°C., a die temperature kept at 220° C., and a vent hole, to produce therubber modified thermoplastic styrenic resin composition (C-6) in pelletform. The diameter of rubber particle is 0.31 μm, and the preparation ofmodified thermoplastic styrenic resin composition (C-6) and physicalproperties are shown in Table 6.

EXAMPLE 9 Preparation of Rubber Modified Thermoplastic Styrenic ResinComposition (C-7)

[0092] The procedure of Example 8 is repeated except that the styreniccopolymer (A-1) is replaced by styrenic copolymer (A-3), and thetemperature of the barrel and die of the extruder are controlled at220-240° C. and 240° C., respectively. The preparation of the rubbermodified thermoplastic styrenic resin composition (C-7) and physicalproperties are shown in Table 6.

EXAMPLE 5 Preparation of Rubber Modified Thermoplastic Styrenic ResinComposition (C-8)

[0093] The procedure of Example 6 is repeated except that the styreniccopolymer (A-1) is replaced by styrenic copolymer (A-6), and thepreparation of thermoplastic styrenic resin composition (C-8) andphysical properties are shown in Table 6.

COMPARATIVE EXAMPLE 6 Preparation of Rubber Modified ThermoplasticStyrenic Resin Composition (C-9)

[0094] The procedure of Example 8 is repeated except that the styreniccopolymer (A-1) is replaced by styrenic copolymer (A-6), and thepreparation of the rubber modified thermoplastic styrenic resincomposition (C-9) and physical properties are shown in Table 6.

[0095] The standards of analysis for all the physical propertied of thepractice examples and comparative examples in this invention are asfollows:

1. Composition of Thermoplastic Styrenic Resin Composition

[0096] It is analyzed with Fourier Transform Infrared Spectrometermanufactured from Nicolet Company, the series No. is Nexus 470. Therubber content of thermoplastic styrenic resin composition (rubbermodified thermoplastic styrenic resin composition is also includedbelow) is in the unit of weight %. The amount of unit derived from BMImonomer is calculated by use of the mass balance of the raw materialsadded in the polymerization, the conversion of monomers and thecomposition of the recovered volatiles.

2. Residual BMI Monomer

[0097] The thermoplastic styrenic resin composition is dissolved intetrahydrofuran and then the solution is analyzed with gas chromatographequipped with flame ionization detector manufactured from HewlettPackard Company, the series No. is 6890A. If the residual Bismaleimide(BMI) monomer is less than 2 ppm, it will be shown with N.D (NonDetectable).

3. MZ and MW

[0098] It is analyzed by gel permeation chromatograph (GPC) equippedwith differential refractometer refraction detection and lightscattering detection manufactured from Water Company. The conditions foranalysis are as follow:

[0099] Column: KD-806M

[0100] Detector: Water RI-2410

[0101] Moving Phase: THF (Flow speed: 1.0 cc/min)

4. Branching Ratio (gM)

[0102] It is analyzed by use of a combination of gel permeationchromatograph (GPC)${g\quad M} = \frac{\left( r^{2} \right)_{b}}{\left( r^{2} \right)_{l}}$

[0103] manufactured from Water company and a multi-angle laser lightscattering(MALLS) manufactured from Wyatt Technology company, in series,to achieve the rotating radius of branching molecule and linear moleculeat a molar mass of 1×10⁶ g/mol, and then the branching ratio (gM) can becalculated in accordance with the following equation.

[0104] (r²)_(b): the rotating radius of branching molecule

[0105] (r²)₁: the rotating radius of linear molecule

5. MI (Melt Flow Index)

[0106] It is analyzed in accordance with ASTMD-1238 at a testtemperature of 220° C. and a load of 10 kg. The value obtained is in theunit of g/10 min.

6. Maximum Extension Stress

[0107] Please referring to FIG. 1, which is used for the analysis ofmaximum extension stress. The instrument is heated by a heater 10. Hotnitrogen gas, which is heated by heater 10, is introduced through outlet50, in the outside of the discharge port of capillary rheometer 20 is apair of rollers, called the first pair of roller 30, to draw the meltedresin 90. For the transportation of the melted resin 90 to outlet 50,another pair of rollers 40 is installed between the first pair ofrollers 30 and the outlet 50, which is named the second pair of rollers40. In this way, the melted resin after the first pair of roller 30 willbe received by the second pair of rollers 40 and then transported tooutlet 50 to avoid flowing to other locations. The first pair of rollersis equipped with a load cell to detect the drawing force (Pa), which isdefined as extension stress. The analysis is operated at a shear rate of0.1-0.5 l/sec, under 1 50° C., N₂ atmosphere. The change of melt tensionof the resin is indicated as the change of extension stress. If the melttension is increased, the extension stress can be raised.

7. Color

[0108] The color of the resin is direct analyzed with calorimetermanufactured from Nippon Denshoku, and the series No. is NDJ-300A. Thedimensions of quartz cell is 5.5 cm×4.0 cm×2.4 cm.

8. Heat Stability (Δ YI)

[0109] The thermoplastic styrenic resin composition is injection-moldedat a cylinder temperature of 230° C. by a injection molded machine witha capacity of 4.2 oz (117.6 g) manufactured from Zhenxiong Company. Theinjection-molded item is a disk with a thickness of ⅛″ and a diameter of5 cm. The disk is then heated in an oven at 200° C. for 2 hours. Theyellow index (YI) before or after heating is analyzed with colorimetermanufactured from Datacolor International Company, and the series No. isSpectraflash 500.

Δ YI=YI(after heating)−YI(before heating)

9. Wall Thickness Uniformity

[0110] The thermoplastic styrenic resin composition is extruded to forma sheet of 500 mm×500 mm×2 mm by single screw extruder manufactured fromHitachi Zosen (90 mm) at a cylinder temperature of 235° C., which isintroduced to a vacuum forming machine at 160° C. to produce an innerwall of refrigerator with a vacuum forming. The wall thickness of theproduct is analyzed at 10 different spots. The difference between themaximum and minimum is then calculated.

[0111] O: thickness uniformity is good, the difference between themaximum and minimum is less than 0.5 mm

[0112] x: thickness uniformity is bad, the difference between themaximum and minimum is above 0.5 mm

10. The Gloss on the Surface of Injected Products after Painting Process

[0113] The thermoplastic styrenic resin composition is molded at acylinder temperature of 230° C. by an injection machine with a capacityof 4.2 oz (117.6 g) manufactured from Zhenxiong Company. Theinjection-molded item is a 15 cm×7 cm×0.3 cm plate, which is thenpainted with acrylic paint for gloss observation.

[0114] O: gloss is good

[0115] x: gloss is bad

11. Contaminations

[0116] A film with a thickness of 0.3 mm and a diameter of 200 mm isshaped with 10 g of the above-mentioned thermoplastic styrenic resincomposition by heating press and then the number of contaminations areobserved.

12. Weight-Average Particle Diameter

[0117] The weight average particle diameter of rubber particle isdetermined by means of a relatively thin section of resin which is dyedprimarily and which is then photographed by a transmission electronmicroscope. There are about 200-1000 dispersed rubber particlespresented on the photograph, and the particle diameter is determinedindividually. The weight average particle diameter which is based on200-1000 rubber particles, can be calculated through the followingformula:

Weight Average Particle Diameter=Σ niDi ⁴ /ΣniDi ³

[0118] ni=the number of the rubber particle with a diameter of Di

[0119] As shown in Table 1, the thermoplastic styrenic resin compositionmanufactured in the present invention is excellent in processability.The rubber modified thermoplastic styrenic resin composition of thepresent invention gives a good heat stability, impact strength, fluidityand other mechanical properties. In addition, it also gives a uniformwall thickness, and the gloss on the surface of injected products afterpainting process is excellent. All these are shown in Table 2 and Table6. The thermoplastic styrenic resin composition and the rubber modifiedthermoplastic styrenic resin composition in this invention areapplicable for electric and electronic articles and they are especiallyapplicable for the forming and processing of refrigerator plates. So,the thermoplastic styrenic resin composition and the rubber modifiedthermoplastic styrenic resin composition of the present invention isbeneficial to the industry is also commercially valuable.

[0120] It is apparent to those skill in the art that the foregoingdescriptions are merely the preferred embodiments and examples. Thescope of the present invention is not to be limited by the specificembodiments and examples herein disclosed. Any equivalent variations ormodifications, which are performed within the spirit disclosed by thepresent invention, are intended to fall within the scope of the presentinvention.

What is claimed is:
 1. A thermoplastic styrenic resin compositioncomprises a styrenic copolymer (A), which is comprising, 15-100 parts byweight of a unit derived from a styrenic monomer (i-1), 0-45 parts byweight of a unit derived from a vinyl cyanide monomer (i-2), 0-40 partsby weight of a unit derived from a copolymerizable vinyl monomer (i-3)other than the above monomers, and 0.0005-1.0 parts by weight of a unitderived from a polyfunctional maleimide monomer, all based on 100 partsby weight of the total amount of (i-1) to (i-3).
 2. A thermoplasticstyrenic resin composition as claimed in claim 1, wherein thecopolymerizable vinyl monomer is selected from ester of acrylic acid,ester of methacrylic acid and monofunctional maleimide monomer.
 3. Athermoplastic styrenic resin composition as claimed in claim 1, whereinthe amount of the unit derived from a copolymerizable vinyl monomer is2-40 parts by weight.
 4. A thermoplastic styrenic resin composition asclaimed in claim 1, wherein the polyfunctional maleimide monomer isselected from bismaleimide.
 5. A styrenic resin copolymer (A) as claimedin claim 1, wherein the amount of the residual polyfunctional maleimidemonomer is less than 100 ppm.
 6. A thermoplastic styrenic resincomposition according with claim 1, the branching ratio (gM)${g\quad M} = \frac{\left( r^{2} \right)_{b}}{\left( r^{2} \right)_{l}}$

is the range of 0.45-0.95, wherein: (r²)_(b): the rotating radius ofbranching molecule (r²)₁: the rotating radius of linear molecule
 7. Arubber modified thermoplastic styrenic resin composition comprises astyrenic copolymer (A) as the continuous phase comprising, 15-100 partsby weight of a unit derived from a styrenic monomer (i-1), 0-45 parts byweight of a unit derived from a vinyl cyanide monomer (i-2), 0-40 partsby weight of a unit derived from a copolymerizable vinyl monomer (i-3)other than the above monomer, and 0.0005-1.0 parts by weight of a unitderived from a polyfunctional maleimide monomer, all based on 100 partsby weight of the total amount of (i-1) to (i-3), and rubber particle (B)as the dispersed phase wherein the rubber content of the rubber modifiedthermoplastic styrenic resin composition is in the range of 1-40 weight%.
 8. A rubber modified thermoplastic styrenic resin composition asclaimed in claim 7, wherein the residual polyfunctional maleimidemonomer is less than 100 ppm.
 9. A rubber modified thermoplasticstyrenic resin composition as claimed in claim 7, the${g\quad M} = \frac{\left( r^{2} \right)_{b}}{\left( r^{2} \right)_{l}}$

branching ratio (gM) is in the range of 0.45-0.95, wherein: (r²)_(b):the rotating radius of branching molecule (r²)₁: the rotating radius oflinear molecule
 10. A rubber modified thermoplastic styrenic resincomposition as claimed in claim 7, wherein the polyfunctional maleimidemonomer is selected from bismaleimide.